I can't tell the difference

I have a primate I21 integrated amp, bowers and wilkins cm5 speakers, and a slim devices squeezebox. I recently purchased a musialcal fidelity v-dac thinking the squeezebox's dac might be my weak spot. I've done a blind comparison between the sb3's dac and the v-dac but I can't tell the difference between the two.

I really thought that the v-dac should have been a significant upgrade seeing as how it costs the same as the sb3 which has a lesser burr-brown chip and a ton of other componets where with the v-dac you are just paying for the dac and nothing else.

Should I be able to hear the difference here? How much do I need to spend to upgrade my source?